Exam-style question
Try this first
Which of the following is true about the phase relationship between input and output in a non‑inverting amplifier?.
- A.The output is 180° out of phase.
- B.The output is 90° out of phase.
- C.The output is in phase.
- D.The output phase depends on the supply voltage.
Model answer
What a good answer should say
- The output is in phase.
Explanation
Why this works
Initial state: V_in is applied to the + input. Step‑by‑step execution: 1.
Negative feedback forces the op‑amp to adjust V_out until the − input equals V_in. 2.
Because the op‑amp does not introduce a phase shift in this configuration, the output voltage rises or falls in the same direction as the input. Final state: V_out changes synchronously with V_in.
Conclusion: The output is in phase with the input in a non‑inverting amplifier.
Common mistake
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